Optical signal processing package structure

ABSTRACT

A package structure and method of forming the same are provided. The package structure includes a first die, a second die, a wall structure and an encapsulant. The second die is electrically bonded to the first die. The wall structure is laterally aside the second die and on the first die. The wall structure is in contact with the first die and a hole is defined within the wall structure for accommodating an optical element insertion. The encapsulant laterally encapsulates the second die and the wall structure.

BACKGROUND

Optical signal processing has been widely used in many applications inrecent years, particularly the use of optical fiber-related applicationsfor signal transmission.

Optical signal processing may be combined with electrical signalprocessing for full-fledged signal processing. For example, opticalfibers may be used for long-range signal transmission, and electricalsignals may be used for short-range signal transmission as well as forprocessing and controlling. Accordingly, devices incorporating opticalcomponents and electrical components, or packages including both ofoptical dies and electronic dies are used for the conversion betweenoptical signals and electrical signals, and for the processing ofoptical signals and electrical signals.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1A to FIG. 1K are schematic cross-sectional views illustrating amethod of manufacturing a package structure according to a firstembodiment of the disclosure.

FIG. 2A to FIG. 2D are schematic cross-sectional views illustrating amethod of manufacturing a package structure according to a secondembodiment of the disclosure.

FIG. 3A illustrates a top view of a wall structure according to someembodiments of the disclosure.

FIG. 3B and FIG. 3C are partial top views of a package structureaccording to some embodiments of the disclosure.

FIG. 4A is a schematic cross-sectional view illustrating a packagestructure according to alternative embodiments of the disclosure.

FIG. 4B is a partial top view of a package structure according toalternative embodiments of the disclosure.

FIG. 5 illustrates a top view of an encapsulant, a wall structure and afilling material of an intermediate stage in the manufacturing of apackage structure according to some embodiments of the disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a second feature over or on a first feature in the description thatfollows may include embodiments in which the second and first featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the second and first features,such that the second and first features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath”, “below”, “lower”,“on”, “above”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the FIGs. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe FIGs. The apparatus may be otherwise oriented (rotated 90 degrees orat other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Other features and processes may also be included. For example, testingstructures may be included to aid in the verification testing of the 3Dpackaging or 3DIC devices. The testing structures may include, forexample, test pads formed in a redistribution layer or on a substratethat allows the testing of the 3D packaging or 3DIC, the use of probesand/or probe cards, and the like. The verification testing may beperformed on intermediate structures as well as the final structure.Additionally, the structures and methods disclosed herein may be used inconjunction with testing methodologies that incorporate intermediateverification of known good dies to increase the yield and decreasecosts.

FIG. 1A to FIG. 1K are schematic cross-sectional views illustrating amethod of manufacturing a package structure according to a firstembodiment of the disclosure.

Referring to FIG. 1A, a die 10 is provided, the die 10 may be one of thedies included in a wafer. The wafer may include a plurality ofsubstantially identical dies 10 arranged as an array, and the number ofthe dies 10 is not limited in the disclosure. In some embodiments, thedie 10 is a photonic die which has function of receiving opticalsignals, transmitting the optical signals inside photonic die,transmitting the optical signals out of photonic die 10, andcommunicating electronically with electronic die 20. Accordingly,photonic die 10 is also responsible for the Input-Output (IO) of theoptical signals.

In some embodiments, the die 10 includes a substrate 100, a plurality ofconductive vias 101, an interconnection structure 104, conductive pads105, connectors 107 and passivation layers 106 and 108. The substrate100 may be made of semiconductor, glass, ceramic, or dielectric. Forexample, the substrate 100 may include a bulk semiconductor substrate orthe like, which may be doped (e.g., with a p-type or an n-type dopant)or undoped. In some embodiments, the substrate 100 is a siliconsubstrate or other type of semiconductor substrate. Other types ofsubstrate, such as a multi-layered or gradient substrate may also beused. In some embodiments, the material of the substrate 100 may includesilicon, germanium, a compound semiconductor including silicon carbide,gallium arsenic, gallium phosphide, indium phosphide, indium arsenide,and/or indium antimonide, an alloy semiconductor including SiGe, GaAsP,AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP, the like, or combinationsthereof.

In some embodiments, the substrate 100 has a plurality of integratedcircuit devices formed therein and/or thereon. The devices may be activedevices, passive devices, or combinations thereof. In some embodiments,the devices include, for example, transistors, capacitors, resistors,diodes, photodiodes, fuse devices, photonic devices or the like, orcombinations thereof. In some other embodiments, the die 10 is free ofactive devices while including passive devices.

The interconnection structure 104 is formed over the devices of thesubstrate 110. In some embodiments, the interconnection structure 104includes multi-layers of conductive features 103 formed in a dielectricstructure 102. The conductive features 103 electrically connect thedevices in and/or on the substrate 110, so as to form a functionalcircuit. The dielectric structure 102 may include a plurality ofdielectric layers. In some embodiments, the dielectric structure 102 isan inorganic dielectric structure. Alternatively, the dielectricstructure 102 may include organic dielectric material. For example, thematerial of the dielectric structure 102 may include silicon oxide,silicon nitride, silicon oxynitride, silicon carbide, low-K dielectricmaterial, such as un-doped silicate glass (USG), phosphosilicate glass(PSG), boron-doped phosphosilicate glass (BPSG), fluorinated silicaglass (FSG), SiO_(x)C_(y), Spin-On-Glass, Spin-On-Polymers, siliconcarbon material, compounds thereof, composites thereof, combinationsthereof, or the like.

The conductive features 103 may include multiple layers of metal linesand vias (not shown) interconnected to each other. The metal lines andvias include conductive materials, such as metal, metal alloy or acombination thereof. For example, the conductive material may includetungsten (W), copper (Cu), copper alloys, aluminum (Al), aluminumalloys, or combinations thereof.

The pads 105 may be electrically connected to a top conductive featureof the interconnection structure 104, and further electrically connectedto the devices formed on the substrate 100 through the interconnectionstructure 104. The material of the pads 105 may include metal or metalalloy, such as aluminum, copper, nickel, or alloys thereof.

The passivation layer 106 is formed over the substrate 110 and covers aportion of the pads 105. The material of the passivation layer 106 mayinclude silicon oxide, silicon nitride, silicon oxynitride, or acombination thereof. Alternatively, the passivation layer 106 mayinclude a polymer material such as photosensitive polybenzoxazole (PBO),polyimide (PI), benzocyclobutene (BCB), a combination thereof, and/orthe like. Portions of the pads 105 are exposed by the passivation layer106 for further electrical connection. The connectors 107 are formed onand electrically connected to the pads 105 exposed by the passivationlayer 106. The connector 107 includes solder bumps, gold bumps, copperbumps, copper posts, copper pillars, or the like. The passivation layer108 is formed on the passivation layer 106 and laterally aside theconnectors 107. The material of the passivation layer 108 may beselected from the same candidate material of the passivation layer 106.The passivation layer 108 may partially or completely cover sidewalls ofthe connectors 107.

In some embodiments, the die 10 includes a plurality of conductive vias101. The conductive vias 101 are formed in the substrate 100 andelectrically connected to the conductive features 103 of theinterconnect structure 104. In some embodiments, the conductive via 101includes a conductive post and a liner (not shown) surrounding thesidewalls and bottom surface of the conductive via to separate theconductive post from the substrate 100. The conductive post may includecopper, copper alloys, aluminum, aluminum alloys, Ta, TaN, Ti, TiN, CoWor combinations thereof. The liner may include dielectric material, suchas silicon oxide, silicon nitride, or the like. The conductive vias 101may extend into the interconnect structure 104 to be in physical andelectrical contact with the conductive features 103 of the interconnectstructure 104. In some embodiments, the conductive vias 101 are embeddedin the substrate 100 without being revealed at this point.

Still referring to FIG. 1A, in some embodiments in which the die 10 is aphotonic die, the die 10 includes a photonic element region 110 (theregion outlined in dashed line) over the substrate 10. The dielectricfeatures (e.g. the dielectric structure 102 and the passivation layers106, 108) may also extend to photonic element region 110. Variousoptical elements (not shown) may be disposed in the photonic elementregion 110 and/or other suitable region of the die 10. For example, theoptical elements may include waveguides, grating couples, modulatorsand/or the like. In some embodiments, a silicon layer may be formed overthe substrate 100 severing as waveguide(s) for the internal transmissionof optical signals, grating coupler(s) may be disposed on the waveguidesand have the function of receiving and/or transmitting optical signal(e.g. light). For example, the grating coupler may receive opticalsignal from subsequently mounted overlying optical element (e.g. theoptical element 150 shown in FIG. 1K, such as light source or opticalsignal source (e.g. optical fiber)) and transmit the optical signal towaveguide. Alternatively, the grating coupler may receive optical signalfrom the waveguide and transmit the optical signal to overlying opticalelement. Modulator(s) may also be formed on the silicon layer, and areused for modulating the optical signals. It is appreciated that the die10 may include various other devices and circuits that may be used forprocessing and transmitting optical signals and electrical signals,which are also contemplated in accordance with some embodiments of thedisclosure.

Still referring to FIG. 1A, a die 20 is electrically bonded to the die10 through the bonding connectors 113. In some embodiments, the bondingconnectors 113 include solder bumps. In some other embodiments, the die20 may be electrically bonded to the die 10 through fusion bonding,hybrid bonding or a combination thereof. The die 20 may beapplication-specific integrated circuit (ASIC) chip, a system on chip(SoC), an analog chip, a sensor chip, a wireless and radio frequencychip, a voltage regulator chip, a memory chip or the like or anysuitable type of die. In some embodiments, the die 20 is an electronicdie, and acts as a central processing unit, which includes thecontrolling circuit for controlling the operation of the devices inphotonic die 10. In addition, the die 20 may include the circuits forprocessing the electrical signals converted from the optical signals inthe photonic die 10. The die 20 may also exchange electrical signalswith photonic die 10 through bonding connectors 113, for example.

In some embodiments, the die 20 includes a plurality of connectors 112.The material of the connectors 112 may be selected from the samecandidate materials of the connectors 107. The bonding connectors 113are disposed between the connectors 112 and the connectors 107 toprovide the electrical connection between the die 20 and the die 10.Similar to the die 10, the die 20 may also include a semiconductorsubstrate, various devices, an interconnection structure and a pluralityof conductive pads and passivation layers (no shown), and the materialand structure of these components are similar to those described withrespect to the die 10. In some embodiments, the die 20 is bonded to thedie 10 in a face-to-face configuration, and the back side (i.e.substrate) of the die 20 faces upward, but the disclosure is not limitedthereto. It is noted that, one die 20 is shown to be bonded to the die10 for illustration, but the disclosure is not limited thereto.According to some embodiments of the disclosure, a plurality of dies maybe bonded to the die 10, the number of the dies is not limited in thedisclosure, and the plurality of dies may be the same type of the diesor different types of dies.

An underfill layer 115 may be formed to fill the space between the die20 and the die 10 and laterally surround the connectors 107, the bondingconnectors 113 and/or the connectors 112. In some embodiments, theunderfill layer 115 may further extend to cover sidewalls of the die 20.

Still referring to FIG. 1A, a wall structure 120 is formed on the die10. In some embodiments, the wall structure 120 includes polymermaterial and may also be referred to as a polymer wall. For example, thepolymer material may include PI, acrylic, epoxy, or the like, orcombinations thereof. In some embodiments, the material of the wallstructure 120 is free of filler. However, the disclosure is not limitedthereto. In some other embodiments, polymer material having fillersdistributed therein may also be used. The forming method of the wallstructure 120 may include dispensing and curing processes. FIG. 3Aillustrates a top view of the wall structure 120 according to someembodiments of the disclosure. Referring to FIG. 1A and FIG. 3A, in someembodiments, when viewed in the top view, the wall structure 120 isring-shaped, such as rectangular ring-shaped, but the disclosure is notlimited thereto. In alternative embodiments, the wall structure 120 maybe square ring-shaped, circular or oval ring-shaped, or the like, or anyother suitable ring-shaped. In some embodiments, the wall structure 120is formed to be enclosed and hollow ring-shaped.

The wall structure 120 includes a hole (e.g. through hole) 122 enclosedby inner sidewalls of the wall structure 120. The hole 122 may also bereferred to as a cavity. In some embodiments, the wall structure 120 isdisposed directly over the photonic element region 110 of the die 10,and the hole 122 may be directly over the photonic element (e.g. gratingcoupler) of the die 10. In some embodiments, the die 10 may include oneor more corresponding holes (not shown) within the photonic elementregion 110 and directly underlying the hole 122 of the wall structure120. The one or more holes in the photonic element region 110 maypenetrate through the dielectric features and expose the photonicelement (e.g. grating coupler) of the die 10. The hole 122 and/or theone or more holes in the photonic element region 110 may also bereferred to as grating coupler (GC) holes. In some embodiments, the topview of the hole in the photonic element region 110 may be circularshaped, oval shaped, or the like or any other suitable shaped.

In some embodiments, as shown in FIG. 3A, a plurality of wall structures120 may be formed on the die 10, and the plurality of wall structures120 may be arranged as a line, a row, or an array or randomly arranged.The number and the arrangement of the wall structures 120 shown in thefigures are merely for illustration, and the disclosure is not limitedthereto. The number and the arrangement of the wall structures 120 maybe adjusted according to product design and requirement.

As shown in FIG. 1A, in some embodiments, the wall structure 120 isformed to have a height higher than that of the die 20, but thedisclosure is not limited thereto. In alternative embodiments, theheight of the wall structure 120 may be substantially the same as orlower than the height of the die 20. In some embodiments, the top of thewall structure 120 includes a rounded or arced portion, but thedisclosure is not limited thereto.

Referring to FIG. 1B, thereafter, a filling material 124 is formed tofill into the hole 122 of the wall structure 120. In some embodiments,the filling material 124 also fills into the GC holes of the die 10underlying the hole 122. The filling material 124 may be different fromthe material of the wall structure 120. Alternatively, the fillingmaterial 124 may include material(s) similar to the material(s) of thewall structure 120, while the proportion of respective material(s) inthe filling material 124 and the wall structure 120 are different, suchthat the filling material 124 and the wall structure 120 exhibitdifferent properties. In some embodiments, the filling material 124includes polymer, such as PI, acrylic, epoxy or the like or combinationsthereof. The forming method of the filling material 124 may includedispensing and curing processes. In some embodiments, the fillingmaterial 124 is dispensed within and substantially fills up the hole 122of the wall structure 120, and is not dispensed outside the outersidewalls of the wall structure 120. The topmost surface of the fillingmaterial 124 may be slightly lower than or substantially coplanar withthe topmost surface of the wall structure 120.

Referring to FIG. 1C, thereafter, an encapsulant 126 is formed on thedie 10 to encapsulate the die 20, the underfill layer 115, the wallstructure 120 and the filling material 124. The material of theencapsulant 126 is different from the filling material 124. In someembodiments, the encapsulant 126 includes a molding compound, a moldingunderfill, a resin such as epoxy, a combination thereof, or the like. Insome other embodiments, the encapsulant 126 includes a photosensitivematerial such as polybenzoxazole (PBO), polyimide (PI), benzocyclobutene(BCB), a combination thereof, or the like. In alternative embodiments,the encapsulant 126 includes nitride such as silicon nitride, oxide suchas silicon oxide, phosphosilicate glass (PSG), borosilicate glass (BSG),boron-doped phosphosilicate glass (BPSG), a combination thereof, or thelike.

In some embodiments, the encapsulant 126 includes a molding compoundwhich is a composite material including a base material (such aspolymer) and a plurality of fillers distributed in the base material.The filler may be a single element, a compound such as nitride, oxide,or a combination thereof. For example, the fillers may include siliconoxide, aluminum oxide, boron nitride, alumina, silica, or the like, orcombinations thereof. In some embodiments, the fillers are sphericalparticles, or the like. The cross-section shape of the filler may becircle, oval, or any other suitable shape. In some embodiments, thefillers include solid fillers, hollow fillers, or a combination thereof.In some embodiments, the encapsulant 126 is formed by an over-moldingprocess and has a top surface higher than the top surfaces of the die20, the wall structure 120 and the filling material 124.

Referring to FIG. 1C and FIG. 1D, the structure shown in FIG. 1C isflipped upside down and attached to a carrier 130. In other words, thestructure is attached to the carrier 130 with the surface of theencapsulant 126 facing the carrier 130. In some embodiments, thestructure may be attached to the carrier 130 through an adhesive layer,such as die attach film (DAF). The carrier 130 may be a glass carrier, aceramic carrier, or the like. The carrier 130 may include a releaselayer 128 formed thereon. In some embodiments, the release layer 128 maybe formed of an adhesive such as an Ultra-Violet (UV) glue, aLight-to-Heat Conversion (LTHC) glue, or the like, or other types ofadhesives. The release layer 128 may be decomposable under the heat oflight to thereby release the carrier 130 from the overlying structuresin subsequent processes.

Still referring to FIG. 1C and FIG. 1D, after attaching to the carrier130, a back-side grinding process is performed to remove a portion ofthe substrate 100, so as to reveal the conductive vias 101. As such, theconductive vias 101 penetrate through the substrate 100 and may also bereferred to as through substrate vias (TSVs).

Referring to FIG. 1E, a redistribution layer (RDL) structure andconductive terminals are then formed on the die 10. In some embodiments,after the TSVs 101 are revealed and before the formation of RDLstructure, the substrate 100 may further be recessed to have a topsurface lower than the TSVs 101. Thereafter, a dielectric layer 132 maybe formed on the substrate 100 and laterally surrounding the TSVs 101.The dielectric layer 132 may include silicon nitride, for example. Insome embodiments, the formation of the dielectric layer 132 may includethe following processes: a dielectric material layer is formed on thesubstrate 100 to cover sidewalls and top surfaces of the portions of theTSVs 101 protruding from the substrate 100 through a deposition processsuch as chemical vapor deposition (CVD), thereafter, a planarizationprocess (e.g. chemical mechanical polishing (CMP)) is performed toremove excess portion of the dielectric material layer over the topsurfaces of the TSVs 101, so as to reveal the TSVs 101 and form thedielectric layer 132 laterally aside the TSVs 101. In some embodiments,the top surface of the dielectric layer 132 is substantially coplanarwith the top surfaces of the TSVs 101.

Thereafter, a redistribution layer (RDL) structure 136 is formed on andelectrically connected to the die 10. The RDL structure 136 includes adielectric structure 134 and redistribution layers 135 formed in thedielectric structure 134. The dielectric structure 134 may include aplurality of dielectric layers stacked upon one another. The material ofthe dielectric structure 134 may include organic dielectric and/orinorganic dielectric, or a combination thereof. The organic dielectricmay include a polymer material such as polybenzoxazole (PBO), polyimide(PI), benzocyclobutene (BCB), or the like or combinations thereof. Theinorganic dielectric may include silicon oxide, silicon nitride, siliconoxynitride, silicon carbide, or the like or combinations thereof. Theredistribution layers 135 include conductive materials. The conductivematerials include metal such as copper, nickel, titanium, or the like orcombinations thereof. In some embodiments, the redistribution layers 135include one or more layers of conductive traces and vias connected toeach other. It is noted that, the numbers of the dielectric layers andredistribution layers of the RDL structure 136 are not limited in thedisclosure.

The redistribution layers 135 penetrate through the dielectric structure134 to electrically connect to the TSVs 101 of the die 10. In someembodiments, the presence of the dielectric layer 132 may help to avoidthe metal diffusion from the redistribution layer 135 to the substrate100.

Still referring to FIG. 1E, a plurality of connectors 140 are formed onthe RDL structure 136 and electrically connected to the redistributionlayer 135. The connectors 140 may include conductive bumps, solderballs, ball grid array (BGA) bump, controlled collapse chip connection(C4) bumps, or the like or combinations thereof. In some embodiments,the material of the connector 140 includes copper, aluminum, lead-freealloys (e.g., gold, tin, silver, aluminum, or copper alloys) or leadalloys (e.g., lead-tin alloys). The connectors 140 may be formed by ballmounting process, a C4 process, and/or other suitable processes. Theconnectors 140 are electrically connected to the die 10 through the RDLstructure 136, and further electrically coupled to the die 20 throughthe die 10. In some embodiments, the connectors 140 may also be referredto as conductive terminals.

In an illustrative embodiment, the connector 140 includes a conductivebump 138 and a conductive cap 139 on the conductive bump 138. In anembodiment, the conductive bump 138 may be solder free and havesubstantially vertical sidewalls. For example, the conductive bump 138may include copper bump. In some embodiments, a material of theconductive cap 139 includes nickel, tin, tin-lead, gold, silver,palladium, nickel-palladium-gold, nickel-gold, the like, or anycombination thereof. In an embodiment, the conductive cap 139 may besolder cap.

Referring to FIG. 1E and FIG. 1F, in some embodiments, the structureshown in FIG. 1E is flipped upside down and mounted to a tape (e.g. BGtape) 142. Thereafter, the release layer 128 is decomposed under theheat of light, and the carrier 130 is then released from the structureto expose the encapsulant 126. In some embodiments, the BG tape 142includes polyethylene terephthalate (PET). The BG tape 142 may beoptically translucent. In some embodiments, the BG tape 142 is removableafter an exposure of UV light or a heat treatment.

Referring to FIG. 1F and FIG. 1G, a planarization process is thenperformed, so as to expose the filling material 124. In someembodiments, portions of the encapsulant 126, the wall structure 120and/or the filling material 124 may be removed by the planarizationprocess. In some embodiments in which the wall structure 120 includes arounded or arced portion, the rounded or arced portion may be removed(e.g. completely removed) by the planarization process, but thedisclosure is not limited thereto. In some embodiments, portions of thedie 20 may also be removed by the planarization process. Theplanarization process may include a CMP process, for example. After theplanarization process is performed, the top surfaces of the die 20, theencapsulant 126 a, the wall structure 120 a and the filling material 124may be planar and substantially coplanar with each other.

Referring to FIG. 1G and FIG. 1H, the structure shown in FIG. 1G isturned over and mounted to a frame tap 143, and the tape 142 is thenremoved from the structure (e.g. through a heat treatment or UVexposure). Thereafter, a singulation process is performed to form aplurality of substantially identical structures 50 a′. The singulationprocess may be performed along the scribe line SL1. In some embodiments,the scribe line SL1 is configured outside the outer sidewall of the wallstructure 120 a and may pass through the encapsulant 126 a, but thedisclosure is not limited thereto. In alternative embodiments, thescribe line may be aligned with the interface between the wall structure120 a and the encapsulant 126 a (not shown). The wall structure 120 amay be substantially not removed during the singulation process, but thedisclosure is not limited thereto. In alternative embodiments, thescribe line SL1 may pass through the wall structure 120 a, and a portionof the wall structure 120 a may be partially removed by the singulationprocess. It is noted that, merely the scribe line SL1 adjacent to thewall structure 120 a is shown in the figure, while the scribe lineadjacent to the die 20 which may pass through the encapsulant 126 a isnot shown in the figure for the sake of brevity.

Referring to FIG. 1H, in the embodiments in which the singulationprocess is performed along the scribe line SL1, the resulted structure50 a′ may include the die 10, the die 20, the wall structure 120 a, thefilling material 124, the encapsulant 126 a, the RDL structure 136 andthe conductive terminals 140. In some embodiments, the wall structure120 a is ring-shaped (e.g. shaped as a closed ring wall), the outersidewalls of the wall structure 120 a are laterally surrounded by and incontact with the encapsulant 126 a, and the filling material 124 islocated within the hole 122 enclosed by inner sidewalls of the wallstructure 120 a. In other words, the filling material 124 is laterallysurrounded by and in contact with the wall structure 120 a.

Referring to FIG. 1H and FIG. 1I, after the singulation process isperformed, the structure 50 a′ is removed from the frame tape 143.Thereafter, the structure 50 a′ may be electrically coupled to otherpackage component (e.g. package component 145) through the connectors140. The package component 145 may be a circuit substrate, such as aprinted circuit board (PCB). In some embodiments, the package component145 includes a plurality of conductive features 144 which areelectrically connected to the connectors 140 of the structure 50 a′.

In some embodiments, an underfill layer 146 is formed to fill the spacebetween the structure 50 a′ and the package component 145 by, forexample, dispensing and curing processes. The underfill layer 146laterally surrounds the connectors 140. In some embodiments, theunderfill layer 146 may further extend to cover the sidewalls of the RDLstructure 136 and/or the sidewalls of the die 10.

Referring to FIG. 1I and FIG. 1J, thereafter, the filling material 124is removed, such that the hole 122 of the wall structure 120 a (and theholes in the photonic element region 110 of the die 10) are unfilled andrevealed for optical element insertion, and a package structure 50 a isthus formed. In some embodiments, the filling material 124 is removed bywet and/or dry cleaning process. The wet and/or dry cleaning processutilize cleaning agent exhibiting a high removal selectivity ratio ofthe filling material 124 to the adjacent materials (e.g. the wallstructure 120 a, the encapsulant 126 a, the die 20), such that thefilling material 124 is substantially completely removed by the cleaningprocess, while the wall structure 120 a, the encapsulant 126 a and thedie 20 are substantially not consumed during the removal of the fillingmaterial 124. In some embodiments, the cleaning agent used for the wetcleaning process may include KOH, water or the like, or combinationsthereof; the cleaning agent (e.g. chemical gas) used for the drycleaning process may include O₂, CF₄, Ar, or the like or combinationsthereof.

In the embodiments of the disclosure, since the removal of fillingmaterial 124 and reveal of the hole 120 a are performed after thesingulation process, some advantages may be achieved. For example, ifthe hole 120 a is revealed before performing the singulation process,fillers of the encapsulant may fall into the GC holes during thesingulation process, which may negatively affect the subsequentlyoptical element insertion. In the embodiments of the disclosure, sincethe GC holes are protected by the filling material 124 and/or the wallstructure 120 a during the singulation process, the above-describedissue is avoided, and clean GC holes may be obtained for optical elementinsertion. In addition, the wall structure 120 a is used to obtain goodsidewall shape which is also benefit for the subsequently opticalelement insertion. For example, the wall structure 120 a formed bydispensing process may include substantially straight and smoothsidewalls.

Referring to FIG. 1K, in some embodiments, an optical element 150 isinserted into the hole 122 of the wall structure 120 a, so as to beoptically coupled to the optical elements (such as, grating coupler,waveguide, modulator) in the region 110 of the die 10. The opticalelement 150 may include coupler, optical fiber(s), or the like, orcombinations thereof. In some embodiments, the optical element 150includes engaging element(s), or the like (e.g. protrusions) which areconfigured for engaging with the GC holes that are disposed in theregion 110 of the die 10 and underlying the hole 122, so as to implementthe optical element insertion. It is noted that, the shape, size,structure and position of the optical element 150 shown in the figuresare merely for illustration, and the disclosure is not limited thereto.In some embodiments, some portions of the optical element 150 are inphysical contact with the die 10 and/or the wall structure 120, whileother portions of the optical element 150 may be spaced from the die 10and/or the wall structure 120. In some embodiments, additional material(not shown), such as optical adhesive may be used to fix the opticalelement 150 onto the package structure 50 a. In the present embodiment,the optical element 120 is inserted into the hole 122 from the top ofthe package structure 50 a, and such configuration may also be referredto as top-insertion configuration.

As such, a package structure PKG1 is thus formed. The package structurePKG1 includes a package structure 50 a on the substrate 145. In someembodiments, the package structure 50 a includes the die 10, the die 20,the wall structure 120 a, the encapsulant 126 a, the RDL structure 136and the conductive terminals 140. The package structure 50 a furtherincludes the optical elements laterally aside the die 20 and mounted onthe die 10. In some embodiments, the die 10 is a photonic die, and thedie 20 is an electronic die which is electrically coupled to thephotonic die. The optical element 150 is laterally surrounded by thewall structure 120 a and optically coupled to the die 10. The packagestructure PKG1 may also be referred to as a chip-on-wafer-on-substrate(CoWoS) package structure or a CoWoS photonic device, and the die 10 maybe referred to as an interposer.

FIG. 3B is a top view of the package structure 50 a illustrating theposition relation of the wall structure 120 a, the encapsulant 126 a andthe optical element 150. It is noted that, the die 20 is not shown inthe top view for the sake of brevity, and the sizes of the elements inthe top view are not drawn to scale.

Referring to FIG. 1K and FIG. 3B, in some embodiments, the wallstructure 120 a is ring-shaped, such as a closed ring-shaped wall.Although a rectangular ring-shaped wall structure 120 a is illustratedin FIG. 3B, the disclosure is not limited thereto. The wall structure120 a may also be square ring-shaped, circular ring-shaped, ovalring-shaped, or the like, or any other suitable ring-shaped. The wallstructure 120 a is laterally surrounded by and in physical contact withthe encapsulant 126 a. In some embodiments, each side (e.g. each of thefour outer sidewalls) of the wall structure 120 a is laterally coveredby and in physical contact with the encapsulant 126 a. The material ofthe wall structure 120 a may be different from the encapsulant 126 a,and interfaces are existed between the wall structure 120 a and theencapsulant 126 a. In some embodiments, the encapsulant 126 a includes abase material and fillers, while the wall structure 120 a is a polymerwall free of fillers. The wall structure 120 a may include asubstantially homogenous material in its entire structure (e.g. frombottom to top). However, the disclosure is not limited thereto.

In some embodiments, the bottom surface of the wall structure 120 a issubstantially coplanar with the bottom surface of the encapsulant 126 aand in direct contact with the die 10. There may be free of gap or anyother additional material (e.g. adhesive material) between the wallstructure 120 a and the die 10. The top surface of the wall structure120 a may be substantially coplanar with the top surface of theencapsulant 126 a, but the disclosure is not limited thereto.

In some embodiments, as shown in FIG. 1K, the wall structure 120 aincludes a first portion P1 and a second portion P2 which are twoopposite sides of the wall structure 120 a. The first portion P1 iscloser to the die 20 than the second portion P2, and the second portionP2 is adjacent to the edge of the package structure 50 a. In someembodiments, the sizes (e.g. width, height) of the four sides of thewall structure 120 a may be the same or different. For example, the size(e.g. width W1 or height H1) of the first portion P1 may besubstantially the same as or different from the size (e.g. width W2 orheight H2) of the second portion P2. The height H1/H2 of the wallstructure 120 a may be substantially equal to the height H3 of theencapsulant 126 a, but the disclosure is not limited thereto. In someother embodiments, the height H1/H2 of the wall structure 120 a may beless than or larger than the height H3 of the encapsulant 126 a. In someembodiments, the width W1/W2 of the wall structure 120 a may be in arange of 30 μm to 700 μm, the height H1/H2 of the wall structure 120 amay be in a range of 50 μm to 900 μm.

In some embodiments, the encapsulant 126 a includes an edge portion EPcovering sidewall of the second portion P2 of the wall structure 120 a.The width W3 of the edge portion EP may be less than, equal to or largerthan the width W2 of the second portion P2 (or the width W1 of the firstportion P1) of the wall structure 120 a.

In some embodiments, the optical element 150 is disposed in the throughhole 122 of the wall structure 120 a and optically coupled to the die10. The optical element 150 is laterally surrounded by inner sidewallsof the wall structure 120 a and laterally spaced from the encapsulant126 a by the wall structure 120 a therebetween.

FIG. 2A to FIG. 2D are schematic cross-sectional views illustrating amethod of forming a package structure according to a second embodimentof the disclosure. The second embodiment is similar to the firstembodiment, except that the scribe line for the singulation process isconfigured at different position.

Referring to FIG. 2A, in some embodiments, the singulation process isperformed along a scribe line SL2 which is configured at a positiondifferent from the scribe line SL1 shown in FIG. 1H. In someembodiments, the scribe line SL2 is between the inner sidewalls of thewall structure 120 a and may pass through the filling material 124. Inalternative embodiments, the scribe line SL2 may be aligned with theinterface between the inner sidewall of second portion P2 of the wallstructure 120 a and the filling material 124.

Referring to FIG. 2A and FIG. 2B, the singulation process is performedalong the scribe line SL2, so as to form a plurality of packagestructures 50 b′. The singulation process includes performing a waferdicing process or a blade cutting process. In some embodiments, aportion P2 of the wall structure 120 a, a portion of the encapsulant 126covering the portion P2 of the wall structure 120 a, and a portion ofthe filling material 124 are removed by the singulation process, and awall structure 120 b and an encapsulant 126 b are formed. In somealternative embodiments in which the scribe line SL2 is along theinterface between the portion P2 of the wall structure 120 a and thefilling material 124, the singulation process may remove the portion P2of the wall structure 120 b, while the filling material 124 issubstantially not removed during the singulation process. In someembodiments, before the singulation process, the wall structure 120 a isa closed ring-shaped wall structure, and after the portion P2 is removedby the singulation process, the obtained wall structure 120 b becomes anopen ring-shaped wall structure.

Referring to FIG. 2B, after the singulation process is performed, thewall structure 120 b becomes an open ring-shaped wall structure, and asidewall 124 s of the filling material 124 is exposed. FIG. 5illustrates a top view of the wall structure 120 b, the encapsulant 126b and the optical element 150 of FIG. 2B. When viewed in the top viewFIG. 5, three sides of the filling material 124 are laterally surroundedand covered by the wall structure 120 b, while the other side (thesidewall 124 s) of the filling material 124 is exposed. In someembodiments, the sidewall 124 s of the filling material 124 issubstantially aligned with or coplanar with the trim sidewalls S1 of thewall structure 120 b and the sidewall S2 of the encapsulant 126 b alonga YZ plane perpendicular to the top surface of the die 10.

Thereafter, the structure 50 b′ is bonded to the package component 145,and an underfill layer 146 is formed to fill the space between thestructure 50 b′ and the package component 145.

Referring to FIG. 2B and FIG. 2C, the filling material 124 is thenremoved by a cleaning process, and a hole 122 a the wall structure 120 bis revealed for optical element insertion, and a package structure 50 bon substrate 145 is formed. In the present embodiment, since the portionP2 (FIG. 2A) is removed during the singulation process, the enclosedwall structure is open.

Referring to FIG. 2C and FIG. 2D, an optical element 150′ is theninserted into the hole 122 a of the wall structure 120 b to opticallycouple to the die 10. In some embodiments, the optical element 150′ isinserted into the hole 122 a from the lateral side, and suchconfiguration may also be referred to as side-insertion configuration.As such, a package structure PKG2 is formed. In some embodiments, thepackage structure PKG2 includes the package structure 50 b on thesubstrate 145. The package structure PKG2 is similar to the packagestructure PKG1, except that the wall structure 120 b is open ring-shapedand configured for side insertion of the optical element 150′.

FIG. 3C is a top view of the package structure 50 b illustrating theposition relation of the wall structure 120 b, the encapsulant 126 b andthe optical element 150′. It is noted that, the die 20 is not shown inthe top view for the sake of brevity, and the sizes of the elements inthe top view are not drawn to scale.

Referring to FIG. 2D and FIG. 3C, in some embodiments, the wallstructure 120 b is not enclosed. For example, the wall structure 120 bmay be open or partial ring-shaped, U-shaped, or the like. In someembodiments, the wall structure 120 b is open rectangular ring-shaped,so that the wall structure 120 b includes three outer sidewalls, threeinner sidewalls and two trim sidewalls S₁ connecting the outer sidewallswith the inner sidewalls of the wall structure 120 b. The trim sidewallsS1 are located at the opening of the open ring-shaped wall structure.The three outer sidewalls of the wall structure 120 b are surrounded byand in physical contact with the encapsulant 126 b. As the wallstructure 120 b is an open ring-shaped wall, the trim sidewalls S1 ofthe wall structure 120 b are not covered by the encapsulant 126 b andthe exposed surfaces of the trim sidewalls S1 may be substantiallyaligned with or coplanar with the sidewall S2 of the encapsulant 126 balong a YZ plane perpendicular to the top surface of the die 10. Thesizes (e.g. width, height) of the wall structure 120 b and/or the size(e.g. height) of the encapsulant 126 b may be in a substantially thesame range of those described in the first embodiment, which are notdescribed again here.

The wall structure 120 b includes a hole 122 a defined by innersidewalls thereof, and the optical element 150′ is disposed in the hole122 a to be optically coupled to the die 10. In some embodiments, threesides of the optical element 150′ are laterally surrounded by the wallstructure 120 b, while the other sidewall is exposed and may besubstantially aligned with or laterally offset from the sidewall S1 ofthe wall structure 120 b and/or the sidewall S2 of the encapsulant 126b.

FIG. 4A illustrates a cross-sectional view of a package structure PKG3according some alternative embodiments of the disclosure. FIG. 4B is topview of a package structure 50 c included in the package structure PKG3according to the alternative embodiments of the disclosure. Theformation of the package structure PKG3 is similar to that of thepackage structure PKG1, except that the scribe line SL1 (FIG. 1H) forthe singulation process of the package structure 50 c is aligned with aninterface between the wall structure 120 a and the encapsulant 126 a orpass through the wall structure 120 a.

Referring to FIG. 4A and FIG. 4B, in some embodiments, the wallstructure 120 a is ring-shaped, such as a closed ring-shaped wall. Thewall structure 120 a may include four sides, wherein three sides of thewall structure 120 a are laterally surrounded by the encapsulant 126 a,while the other side of the wall structure 120 a is exposed. In someembodiments, the sidewall of the portion P2 of the wall structure 120 ais exposed by the encapsulant 126 a and may be substantially alignedwith the sidewall of the encapsulant 126 a in a direction parallel withthe top surface of the die 10.

In the embodiments of the disclosure, a non-removable polymer wall andremoval polymer filling material are used for forming a cavity structurewhich is configured for optical element insertion. The polymer fillingmaterial is removed by cleaning process after the singulation process isperformed. Therefore, the photonic element (e.g. grating coupler) of thephotonic die and GC holes may be well protected by the polymer wall andthe filling material during the manufacturing process. The issue ofencapsulant particles (e.g. fillers) falling into the GC holes duringsingulation process is thus avoided. As such, clean GC holes could beobtained for top-insertion structure or side-insertion structure. Inaddition, a good shape for optical element insertion may be obtained dueto polymer wall formation, and a large process integrate window forCoWoS photonic device may be achieved. The manufacturing process of theembodiments is simplified and manufacturing cost is reduced, therebyimproving the manufacturing yield.

In accordance with some embodiments of the disclosure, a packagestructure includes a first die, a second die, a wall structure and anencapsulant. The second die is electrically bonded to the first die. Thewall structure is laterally aside the second die and on the first die.The wall structure is in contact with the first die and a hole isdefined within the wall structure for accommodating an optical elementinsertion. The encapsulant laterally encapsulates the second die and thewall structure.

In accordance with alternative embodiments of the disclosure, a packagestructure includes a photonic die, an electronic die, a polymer wall, anencapsulant and an optical element. The electronic die is electricallybonded to the photonic die. The polymer wall is disposed on the photonicdie. The encapsulant laterally encapsulates the electronic die and thepolymer wall. The optical element is laterally surrounded by the polymerwall and optically coupled to the photonic die.

In accordance with some embodiments of the disclosure, a method offorming a package structure includes: electrically bonding a second dieto a first die; forming a wall structure on the first die and laterallyaside the second die, wherein a through hole is defined by innersidewalls of the wall structure and exposes the first die; forming afilling material to fill the through hole within the wall structure;forming an encapsulant to encapsulate the second die, the wall structureand the filling material; and removing the filling material to revealthe through hole within the wall structure for accommodating an opticalelement.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the disclosure.Those skilled in the art should appreciate that they may readily use thedisclosure as a basis for designing or modifying other processes andstructures for carrying out the same purposes and/or achieving the sameadvantages of the embodiments introduced herein. Those skilled in theart should also realize that such equivalent constructions do not departfrom the spirit and scope of the disclosure, and that they may makevarious changes, substitutions, and alterations herein without departingfrom the spirit and scope of the disclosure.

What is claimed is:
 1. A package structure, comprising: a first die; a second die, electrically bonded to the first die; a wall structure, disposed laterally aside the second die and on the first die, wherein the wall structure is in contact with the first die and a hole is defined within the wall structure for accommodating an optical element; and an encapsulant, laterally encapsulating the second die and the wall structure wherein the wall structure is in contact with the encapsulant and is separated from the second die by a portion of the encapsulant disposed between the wall structure and the second die.
 2. The package structure of claim 1, wherein a bottom surface of the wall structure is substantially coplanar with a bottom surface of the encapsulant, and a topmost surface of the wall structure is substantially level with a topmost surface of the encapsulant.
 3. The package structure of claim 1, wherein the hole is defined by inner sidewalls of the wall structure and the first die is a photonic die optically coupled with the optical element inserted in the hole.
 4. The package structure of claim 3, wherein the photonic die comprises a photonic element region.
 5. The package structure of claim 4, wherein the hole exposes the photonic element region of the photonic die, and the optical element disposed in the hole within the wall structure is optically coupled to at least one photonic element in the photonic element region of the photonic die.
 6. The package structure of claim 1, wherein the wall structure includes a polymer wall.
 7. The package structure of claim 1, wherein the wall structure is a closed ring-shaped wall.
 8. The package structure of claim 7, wherein the encapsulant contacts and wraps around each outer sidewall of the wall structure.
 9. The package structure of claim 7, wherein the encapsulant contacts and wraps around a first outer sidewall of the wall structure, while a second outer sidewall of the wall structure that is opposite to the first outer sidewall is exposed from the encapsulant.
 10. The package structure of claim 1, wherein the wall structure is an open ring-shaped wall.
 11. The package structure of claim 10, wherein an outer sidewall of the wall structure is not covered by the encapsulant.
 12. A package structure, comprising: a photonic die; an electronic die, electrically bonded to the photonic die; a polymer wall, disposed on the photonic die; an encapsulant, laterally encapsulating the electronic die and the polymer wall, wherein the polymer wall is in contact with the encapsulant and is separated from the electronic die by a portion of the encapsulant disposed between the polymer wall and the electronic die; and an optical element, laterally surrounded by the polymer wall and optically coupled to the photonic die.
 13. The package structure of claim 12, wherein the polymer wall is a closed ring-shaped wall having four lateral sidewalls defining a hole within the four lateral sidewalls of the polymer wall, the hole exposes a photonic element region of the photonic die, and the optical element disposed in the hole within the polymer wall is optically coupled to at least a photonic element in the photonic element region.
 14. The package structure of claim 12, wherein the polymer wall is a closed ring-shaped wall having four lateral sidewalls, and at least three lateral sidewalls of the polymer wall are laterally encapsulated by the encapsulant.
 15. The package structure of claim 14, wherein the encapsulant contacts and wraps around each of the four lateral sidewalls of the polymer wall.
 16. The package structure of claim 14, wherein the four lateral sidewalls comprise a first outer sidewall and a second outer sidewall of the polymer layer, and the encapsulant contacts the first outer sidewall of the polymer wall.
 17. The package structure of claim 16, wherein the second outer sidewall is opposite to the first outer sidewall and is exposed from the encapsulant.
 18. The package structure of claim 12, wherein the polymer wall is an open ring-shaped wall having three lateral sidewalls and the three lateral sidewalls of the polymer wall are laterally encapsulated by the encapsulant, and a side surface of a fourth lateral sidewall of the wall structure is exposed by the encapsulant.
 19. The package structure of claim 12, wherein a bottom surface of the polymer wall is substantially coplanar with a bottom surface of the encapsulant.
 20. The package structure of claim 12, wherein a topmost surface of the polymer wall is substantially level with a topmost surface of the encapsulant. 